Method of imparting alpha multicolored effect to coal



Patented Mar. 27, 1934 UNITED STATES PATENT OFFICE METHOD OF IMZPARTING A MULTICOLORED EFFECT TO COAL Jersey No Drawing. Application March 19, 1930,

Serial No. 437,275

'1 Claims. (01. 44-6) This invention relates to processes for producng rapidly and cheaply a multicolor effect on coal and to the products thereof. For convenlence of expression, the colored effects will be designated hereinafter as rainbow.

These rainbow effects are obtained according to my invention not by the application to the coal of suspensions of previously produced mixtures of colors, lakes or pigments, but by bringing the coal 0 in contact with a suitable solution from which is deposited by chemical or physical reactions, a very thin adherent colored film. If this film could be detached from the coal and be viewed by transmitted light, it would probably appear to be monochromatic or of a single color. When the colored film on the surface of the coal is I sufiicientlyvthin, it will exhibit by reflected light or as one would naturally view it a multicolored or rainbow effect, due, presumably, to the interference of the light waves reflected from the upper and lower surfaces of the colored film;

The rainbow effect is not dependent on the intrinsic color of the deposit, although the brilliancy of the rainbow display seems to be governed somewhat by the actual color of the deposit. For

' example, blue deposits give brighter rainbow efiects than brown or reddish brown deposits.

'The deposition of the colored film may be brought about in various ways, of which the ac- 39 companying examples are illustrative. Examples (a) illustrate the deposition of color and production of the rainbow effect by chemical reduction of the applied solution apparently by the surface constituents'of the coal. Other examples (b) show deposition of the color by oxidation of the applied solution, and further examples (0) the deposition of the color from colloidal solutions.

The procedure in respect to examples (a) is as follows:

ferric chloride crystals and 3 pounds of an alkali ferricyanide, such as potassium ferricyanide. It

is better to dissolve these salts separately in a little water which can readily be done because they are freely soluble and then add these concentrated solutions to the larger bulk of water.

Either the dry or wet coal is then immersed in this bath for a short time and if desired it can then be washed. The color display appears on the coal while it is still in the bath but shows up more brilliantly after the coal is dry. The immersion time may be as short as thirty seconds if the temperature of the bath is not too low, thus permitting the passage of a large bulk of coal 100 gallons of water add 2.5 pounds of through a standing bath in a continuous operation. A solution like the above can also be sprayed on the coal or be applied to it by other means. The proportions of chemicals used can be varied over wide limits, thus obviating the necessity of rigid control.

The deposit on the coal resulting from the reduction of the ferric ferricyanide or potassium ferric ferricyanide solution prepared as above, is an insoluble film of Prussian blue or related chemical compound, so thin as to produce the rainbow effect as described. The relationship of the different colors can be altered by varying the conditions, for instance orange and yellow can be made predominant, or blue and violet. The film is very adherent.

(2) Another method of producing the rainbow effect by chemical reduction is as follows: Mix together twenty .volumes of a one percent solution of potassium permanganate, ten volumes of a one percent solution of ferric chloride and two volumes of a one percent solution of sulphuric acid. Immerse the coal in this at normal temperature for a minute or more. Remove and allow to dry. A thin brown film of oxides or hydrated oxides of manganese and iron forms on the surface of the coal which by reflected light appears as a rainbow effect. The above proportions of chemicals, and the time and temperature can be widely varied, and the ferric chloride can be omitted or other chemicals added such as aluminum sulphate or sodium bichromate and a rainbow effect can. still be obtained.

The more detailed procedure in regard to example (b) representing the formation of deposits by oxidation reactions is as follows:

(1) Five-tenths of a pound of the dye Ciba blue 23 is vatted with three-tenths of a pound of caustic soda, and one pound of sodium hydro- Jsulphite in 3 gallons of water at 165 F. in much the ordinary way of preparing a solution of the leuco-compound of this dye for coloring textile fibres. The above stock vat" is then diluted with 190 gallons of water which in textile parlance has been sharpened with a very little caustic soda and hydrosulphite of soda. The diluting water can be around 80 to 90 F. and need not be at the usual dyeing temperature for Ciba blue 23. The coal is immersed in the above dye solution for a minute or more until a very thin blue deposit is formed thereon, which if sufficiently thin exhibits the rainbow effect.

Other dyestufis can be used that can be applied similarly; as for example Sulphur Navy blue GL, although the proportions of dye, caustic soda and sodium hydrosulphite may have to be varied.

I have referred to this method of producing rainbow coal as an oxidation reaction, because in textile practice, the true color of a vat dye usually exhibits itself only on oxidation of the soluble leuco-compound. Inasmuch as in the above described method of applying Ciba blue 2B to coal, the formation of the blue film on the coal does actually take place beneath the surface of the vat, the oxidation may be due to occluded air on the surface of the coal, or it may be that the acidity of the coal reduces the alkalinity of the dye solution in immediate contact with the coal suificiently to throw out the color, which does not redissolve.

The more detailed description of examples (0) representing deposits from colloidal solutions, is as follows: Dissolve two pounds of ferric chloride in 100 pounds of water, add a very small amount of hydrochloric acid and heat the solution slowly until a slight opalescence becomes noticeable, then discontinue the heating. Allow the solution to cool and spray or sprinkle it on the coal. On drying, the rainbow effect will appear. The above method can be altered in regard to concentration, heating or additions of protective colloids such as cane or invert sugar.

The preferred process is the one using ferric chloride and potassium ferricyanide because it is fairly cheap, is easy to carry out, the effect is reasonably permanent and because the color display exhibits much brilliancy.

The stability and effectiveness of a standing bath containing ferric chloride and a ferricyanide can be maintained by addition of other chemicals, for instance, soluble chromates and bichromates are helpful in this respect. As is usual in the case of standing baths in continuous operations, the strength of the bath can be maintained by constant or intermittent replenishment with the chemicals which are being removed therefrom by the coal as it passes through the bath.

The methods described are merely illustrations of several different procedures that can be used as I in carrying out my invention. The deposits are adherent in that they cannot readily be washed or rubbed off, and they have a reasonable and sufficiently practical degree of stability and permanency.

Whether the explanations of the reactions which take place are scientifically accurate is immaterial, because the results of the invention are as described.

Various changes may be made in the procedure and materials employed without departing from the invention or sacrificing any of the advantages thereof.

I claim:

1. The method of imparting a multicolored effeet to coal which comprises treating the coal with a solution of ferric chloride and a soluble ferricyanide.

2. The method of imparting a multicolored effect to coal which comprises treating the coal with a solution. of ferric chloride and an alkali ferricyanide.

3. The method of imparting a multicolored effect to coal which comprises treating the coal with a solution of ferric chloride and potassium ferricyanide.

4. The method of imparting a multicolored effect to coal which comprises treating the coal with a solution of a ferric salt and a soluble ferricyanide.

5. The method of imparting a multicolored effect to coal which comprises treating the coal in an acid solution containing an alkali permanganate and ferric chloride.

6. The method of imparting a multicolored effect to coal which comprises treating the coal in an acid solution containing potassium permanganate and ferric chloride.

7. The method of imparting a multicolored effect to coal which comprises treating the coal with a solution containing potassium permanganate, ferric chloride and sulphuric acid.

HARRY S. MORK. 

